Process for reducing the refractory halide content of an alkyl aromatic employing as contact material an alkaline earth metal compound consisting of the oxides and carbonates of calcium



United States Patent 3,497,567 PROCESS FOR REDUCING THE REFRACTORY HA-LIDE CONTENT OF AN ALKYL AROMATIC EM- PLOYING AS CONTACT MATERIAL ANALKA- LINE EARTH METAL COMPOUND CONSISTING OF THE OXIDES AND CARBONATESOF CAL- US. Cl. 260-674 4 Claims ABSTRACT OF THE DISCLOSURE Therefractory chloride content of an alkyl aromatic compound can be reducedby treating said compound with an alkaline earth metal compound, such ascalcium oxide, at elevated temperatures. The process is useful toprepare detergent alkylates having reduced chloride content andtherefore superior properties.

BACKGROUND OF THE INVENTION Chlorine is frequently an undesirableimpurity in certain materials. For example, the presence of chlorine inthe so-called detergent alkylates is undesirable because of itsirritating effect on the skin. One would expect that such undesirablechlorine compounds could be removed by ordinary and well-knowntechniques for the removal of such impurities, for example, by causticscrubbing. Unfortunately this is not true in many instances. It has beenfound, in fact, that the chlorine is frequently chemically bound tocompounds whose freedom from such chlorine is important for successfulcommercial application of said compounds. By the practice of the processdescribed and claimed below it is possible to eliminate these and otherproblems by reducing the chlorine content of chloridecontainingcompounds.

Aromatic compounds such as benzene, xylene, naphthalene, anthracene,etc., can be alkylated with a mixture of primary and secondary normalalkyl monochlorides, wherein the alkyl portion thereof has, for example,from to 16 carbon atoms, to produce an alkyl aromatic mixture. Thismixture is commonly referred to as detergent alkylate, since it can besubsequently sulfonated in known manner to produce a detergent. Thedesired alkylation is typically carried out in the presence of about 3to about 10 weight percent of a Lewis acid, such as aluminum chloride,in which the reaction system can contain from about 5 to about 15 molesof aromatic per mole of alkyl halide. Normal alkylation conditionsinclude temperatures ranging from about 15 to about 70 C., pressuresranging from about 250 mm. Hg to about 100 p.s.i.g. and reaction periodsof about /2 to about 1 /2 hours. Upon completion of the reaction thecatalyst is usually removed as a sludge and the mixture washed free ofhydrogen chloride. The mixture can then be fractionated at atmosphericpressure and temperatures ranging from about 70 to 85 C. to remove anyunreacted aromatic compounds therefrom. Thereafter, it is customary tovacuum distill the mixture, at pressures of from about 1 to about 20 mm.Hg and temperatures ranging from about 100 to about 200 C. to recover,sequentially, unreacted paraffin and the desired alkyl aromaticcompounds or mixtures thereof, termed detergent alkylate. This detergentalkylate frequently contains chlorine which is often undesirable fromthe point of view of the end use of the product. These detergentalkylates can contain from about 100 to about 5000, but in generalcontain from about 100 to about 500, parts per million of chlorine.Those detergents which are to be used in the home for such generalpurposes as dishwashing, general cleaning etc., desirably should not beirritating to the skin. Chlorine containing detergents, which areirritating because of their chlorine content, are consequently lessdesirable for general purpose household use than chloride-freedetergents and in fact soap and detergent manufacturers frequentlyspecify the maximum tolerable chloride content, which detergents ordetergent alkylates purchased by them can have, as less than 50 ppm. Itis thus particularly desirable, prior to sulfonation, to have thedetergent alkylate as free of chlorine as possible.

It is believed that the undesirable chlorine components referred toabove are not merely mixed in with the detergent alkylate but may befirmly attached to some part of a molecule by chemical bonding. Thisassumption is supported by the fact that such techniques as causticscrubbing and distillation results in a product that still contains asignificant quantity of chlorine. Such chlorine is termed hereinrefractory, indicating that it is heat resistant, that it cannot beremoved by distillation.

SUMMARY OF THE INVENTION We have found that the refractory chlorinecontent of an alkyl aromatic compound can be reduced by treating saidcompound with an effective amount of an alkaline earth metal compoundselected from the group consisting of the oxides and carbonates ofcalcium. Calcium oxide is preferred.

As indicated above this process has particular utility in removingrefractory chloride from a detergent alkylate.

The process is quite simply accomplished by merely contacting thematerial which contains refractory chloride with one or more of thedefined alkaline earth metal compounds at a temperature of from about toabout 500 C., preferably from about 200 to about 400 C., at pressureswhich can range from about atmospheric to as high as about 500 p.s.i.g.The process is preferably conducted at atmospheric pressure. The amountof alkaline earth metal compound employed can vary over wide ranges andonly such amount thereof need be used that will be sufficient to obtainthe desired contact with the material containing the refractorychloride. In general, the amount of alkaline earth metal compound thatneed be present relative to the material containing the refractorychloride, on a weight basis, can be from about 10:1 to about 1:10,preferably from about 5:1 to about 1:5. The amount of contact requiredbetween the two can also vary, for example at least about 1 second andpreferably from about 5 to about 10 seconds. The process can beconducted in a wide variety of equipment in either continuous orbatchwise operation. One advantageous aspect of our invention is thatthe process can be run continuously and in a preferred embodiment ahollow tube packed with calcium oxide and heated to the desiredtemperature is used. It should be noted at this point that not allmethods of treatment of materials containing refractory chloride areequivalent, even when the same alkaline earth metal compounds are used.Thus, for example, when a detergent alkylate containing chlorine wasdistilled over calcium oxide, the results obtained were not nearly asgood with respect to halide reduction as were those obtained when thematerial was treated in accordance with the instant process. Theseresults can be seen in Example II.

As will be seen from the following examples, treatment of materialscontaining refractory chloride results in a significant decrease inchlorine content. The precise range of chlorine content of the productmaterial cannot be stated with greater particularity because the actualreduction in chlorine content can be controlled at will by varying suchfactors as Contact time, amount of alkaline earth metal compound etc.

The process of this invention can further be understood by reference tothe following:

DESCRIPTION OF THE PREFERRED EMBODIMENTS These two examples show thatthe chloride content is not significantly reduced by treating chlorinecontaining materials in the usual manner. The examples also lend weightto the theory that the chlorine is in some Way bound to the materialreduction of whose chlorine content is desired.

EXAMPLE I This example illustrates the utility of the process of theinstant invention in reducing the chlorine content of a detergentalkylate.

A detergent alkylate was prepared as follows: Five gallons (14.5kilograms) of C -C normal paraftins (4.6% C 18.2% C 22.2% C 34.3% C20.7% C were chlorinated at 5065 C. in the presence of 150 watt lampsuntil 1.8 kilograms of chlorine added. The product was purged with N toremove excess HCl. The product was then added, over a period of 28minutes, at a temperature of 2122 C. to a mixture of 21.5 kg. of benzeneand 0.4 kg. of AlCl The mixture was stirred for one hour longer and thenthe catalyst layer was drawn off. The solution was washed three timeswith two-gallon aliquots of water, once with one gallon of percent NaOHand twice with two-gallon aliquots of water. The product detergentalkylate was analyzed and found to contain 103 p.p.m. of chlorine.

Fifty grams of the detergent alkylate prepared above were drippedthrough a column, 63.5 cm. x 1.25 cm. I.D., of CaO, heated at 400410 C.over a two hour period. Analysis of the eflluent showed the chlorideconcentration to have dropped to less than 0.5 p.p.m.

EXAMPLE II This example illustrates the proposition that not all methodsof contacting chlorine containing compounds with the alkaline earthmetal compounds useful in the instant invention are capable of givingequivalent results.

Fifty grams of the detergent alkylate prepared in Example I above,containing 103 p.p.m. of chlorine were distilled from 10 g. solid CaOthrough a 12 inch Vigreux column. The product distilled at 120 C. at 1mm. Hg pressure and was found to contain 84 p.p.m. chlorine.

It is thus seen that distilling the chlorine containing material overCaO is not nearly as effective in reducing the chlorine content as istreatment of the same material by the process of the instant invention.

Obviously many modifications and variations of the invention ashereinabove set forth, can be made without departing from the spirit andscope thereof, and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A process for the reduction in the refractory chloride content of analkyl aromatic detergent alkylate which comprises contacting the samesolely with an alkaline earth metal compound selected from the groupconsisting of the oxides and carbonates of calcium at a temperature ofabout 200 to about 500 C.

2. The process of claim 1 wherein said alkaline earth metal compound iscalcium carbonate.

3. The process of claim 1 wherein said alkaline earth metal compound iscalcium oxide.

4. The process of claim 1 wherein said alkyl aromatic detergent alkylateis an alkyl benzene wherein said alkyl has from 10 to 16 carbon atoms.

References Cited UNITED STATES PATENTS 3,274,273 9/1966 Lester et al260666 2,341,567 2/1944 Moriarty 19641 2,481,300 9/1949 Engel 196361,914,668 6/1933 Lachman 208262 PAUL M. COUGHLAN, JR., Primary ExaminerJ. M. NELSON, Assistant Examiner U.S. Cl. X.R. 260671

